I got C/B problems

[bastonjock]

i am toying with the idea of modifying my CB,i was thinking of using a hard nylon for the "doughnut" and machining it to a fine tolerance so that there is no woble in the board.My plan was to increase the width of the cb as far as my trailer will allow and to then place 120 lbs of lead in the bottom of the keel and seal it in with epoxy.

i envisage cutting the top of the cb open and fitting the nylon part and fixing it in place with small tie bars,once the epoxy is poured in then that make for a solid board

I am of the opinion that the wobble of the board inhibits speed and pointing.I was also thinking of doing something similar to the rudders,they just flap about too much and they must cause a drag effect.

The failure of the cb i the photo looks to me that there was no support around the hole,so reinforcing it hopefully would take care of that and there may be the need to reinforce other areas

[DaveB]

I took my centerboard out and was split around the headseam approx 8 inches both sides. I reglassed the seam and by doing so added width to centerboard at the head. I also pored Resin in weep holes and did 360 degree turns to cover all inside of board than added more resin to head inverted than lower unit. took 4 resin mixes to fill the areas I wanted to inforce.
No slop in centerboard now but I also changed to all braided low stretch centerboard line and have to get a roller at the mast 90 degree turning point.
Original centerboard had to much play between the trunk.
I wouldn't add any lead to the centerboard as you won't get it up unless you counterbalance it and thats hard to do since the pivit point is only 8 inches down the centerboard.
If you still want to add lead load the top of centerboard with lead pellits and resin them in, than raise centerboard to feel the center of gravity than add your lead to counter balance.
Dave

i am toying with the idea of modifying my CB,i was thinking of using a hard nylon for the "doughnut" and machining it to a fine tolerance so that there is no woble in the board.My plan was to increase the width of the cb as far as my trailer will allow and to then place 120 lbs of lead in the bottom of the keel and seal it in with epoxy.

i envisage cutting the top of the cb open and fitting the nylon part and fixing it in place with small tie bars,once the epoxy is poured in then that make for a solid board

I am of the opinion that the wobble of the board inhibits speed and pointing.I was also thinking of doing something similar to the rudders,they just flap about too much and they must cause a drag effect.

The failure of the cb i the photo looks to me that there was no support around the hole,so reinforcing it hopefully would take care of that and there may be the need to reinforce other areas

[ALX357]

With regard to the board's " wobble " effect, there is some opinion that it actually helps pointing, and is not a detriment. The board's action has been described as gybing with the tack of the boat. Whether it is a help or a hindrance would be an interesting answer. One thing is certain, is that the board is jammed tight on either tack, and does not " wobble " for the duration of the tack, until it reverses its set and is jammed on the other tack.

Take caution in making the board a tight fit, as it has been repeated many times, both with regard to the pin and hole, and with regard to the board's fit in the trunk. There are several places in these threads that discuss the problems caused by close-tolerance fitting the pin to the board.
Also, the board needs enough room in the trunk to allow some unavoidable marine growth without getting so tight that the board gets too jammed up in the trunk and not free to drop.
This actually happened to the P.O. of my own X, in an Alabama lake, where the growth was extensive and after a few weeks idle time in the slip, the boat's board could not be lowered, as the board and trunk were so mucked up that it would not fall into position when the line was slacked.

[bastonjock]

dave did you nottice any improvement in pointing?

i cant see how the floppy center board would help with pointing,when you are on a close haul the angle of the board would be such that the leading edge is not in line with the center of the boat and therefore presents a greater cross sectional area to the direction of traveland therefore more drag

Ive had a look at "knots shore" web site and the guy has put 150 lbs of lead in his keel,and i had a look at mad mikes board also and he has increased the width of his cb

My plan is,to widen the cb,put some lead i it,fit a nylon bush and put a torpedo shape on the bottom of the cb such as you see on the keels of larger fixed keel boats.

I love my x,i would just like to have it pointing better,i may even try out the "canard" idea

[ALX357]

The flat hull of a Mac has hardly anything to do with which way the boat is going, when under sail. Maybe a bit when heeled over 20, but then the chine is not really a straight line parallel to the centerline of the boat either. It is all in the three fins. If the centerboard cocks slightly to windward when pointing there, it would help to get closer. One owner calls it a "gybeing" centerboard. I recommend more research and investigation before undertaking board mods that may actually degrade performance. More weight in the board seems to be an ok idea for performance, but may result in more damage if grounded accidently in an shallow. Not a concern for deep water only sailors, but the lakes around here are full of shallow areas, being mostly pools behind river dams. The river may be sixty feet deep and look like half a mile wide, but the river channel is only a few hundred feet wide, and the acres of unseen flood-plain underwater banks are often only 3 or 4 feet deep. The transition between channel and plain sometimes is a sudden drop, and when gradual, maybe only across 10 feet, in other words, at any decent speed, instant. Channel markers are sometimes way too conservative, sometimes too liberal, usually too far apart to rely on, and sometimes blown off and floated away. Only a depthfinder or charted GPS can tell when your are in the channel or over the shallows. The Mac X lightweight pivoting board and bungeed rudders have saved my day several times.